File dirvish-lock-vault-against-overlapping-runs.patch of Package dirvish

diff --git a/dirvish.pl b/dirvish.pl
index c2488c4..5a6a0b6 100644
--- a/dirvish.pl
+++ b/dirvish.pl
@@ -451,6 +451,18 @@ scalar @{$$Options{exclude}}
 
 if (!$$Options{'no-run'})
 {
+	$lock_file = "$vault/dirvish/lock_file";
+	if (! -f $lock_file)
+	{
+		open(LOCK, "+>", $lock_file) or seppuku 150, "cannot create $lock_file";
+		printf LOCK $$;
+		close(LOCK);
+	}
+	else
+	{
+		seppuku 151, "$lock_file already exists";
+	}
+
 	mkdir "$vault/$image", 0700
 		or seppuku 230, "mkdir $vault/$image failed";
 	mkdir $destree, 0755;
@@ -755,6 +767,8 @@ if ($$Options{'post-server'})
 	}
 }
 
+unlink($lock_file);
+
 if($status{fatal})
 {
 	system ("rm -rf $destree");